U.S. Pat. No. 4,563,688 issued Jan. 7, 1986 to H. Braun discloses an ink jet print head for continuous-multijet-, ink jet printing. As shown in FIG. 3, the ink jet print head 10 includes an elongated rectangular print head body 12 of high acoustic Q material such as stainless steel. The print head body 12 has a length L that is substantially greater than the other dimensions a and b. The size of the body, with respect to the Q of the material is selected to exhibit a resonant frequency in the longitudinal vibration mode at or very near to the ink drops frequency produced by the ink jet print head 10. The print head body 12 defines an ink reservoir 14, opening in a slot 16 in one end of the print head body 12. An orifice plate 18 defining a plurality of orifices 20 is fixed over the slot 16.
A pump 22 supplies ink under pressure from an ink supply 24 to the reservoir 14 via ink supply tube 26 and an ink supply channel 28 defined by the print head body 12. Ink is forced out of the orifices 20 to define a plurality of ink jets.
An ink outlet channel 30 and ink outlet tube 32 allow the reservoir to be flushed. A pair of piezoelectric transducers 34 (only one of which is shown) are driven by a periodic wave form from an oscillator 36, to excite the longitudinal mode of vibration in the print head body 12. The print head body is mounted by integral tabs 38 located at a nodal plane, so that the vibration of the print head is not transferred to or affected by the mounting. The longitudinal vibration of the print head body is transferred to the orifice plate 18 to thereby stimulate the ink jets to separate uniformly into drops.
The ink supply and outlet tubes 26 and 32 are made from a material selected to have a vibrational impedance substantially different from the print head body 12, such as flexible polymeric material, in an attempt to reduce the effect of the tubes on the vibrations of the print head body.
Although, the use of such polymeric material substantially reduces the effect of the tubes on the vibrational properties of the print head body 12, experiments have determined that there are still some undesirable effects on the vibration of the print head body. For example, relatively small variations in the mass and/or location of the tubes have been observed to cause large changes in the vibrational amplitude and small changes in the longitudinal resonant frequency of the print head body 12. Furthermore, the mounting mechanisms employing the integral tabs 38 requires extremely precise machining of the components to effect accurate placement of the print head, thus increasing the cost of manufacture of the print head.
It is the object of the present invention therefore to provide an improved means for supplying ink to, and mounting for the ink jet print head that solves the problems noted above.